1) Naloxone-stimulated cortisol (naloxone stimulation test) will be superior to a random plasma cortisol as a test of the adequacy of the function of the hypothalamic-pituitary unit.; and 2) the naloxone stimulation test will provide a simple, safe, and reliable alternative to the insulin tolerance test in the evaluation of patients w/suspected central adrenocortical insufficiency. SPECIFIC AIMS: Two major aims 1) To define the cortisol responses to naloxone and identify a cutoff value that will permit the best combination of sensitivity and specificity for the detection of central adrenocortical insufficiency. 2) Compare the diagnostic accuracy of the cortisol response following the administration of naloxone to the basal plasma cortisol level as tests to evaluate the integrity of the HPA axis. The cortisol response to insulin-induced hypoglycemia will be employed as a "gold standard" test.